1. Field of the Invention
The present invention relates to a sheet finisher constructed integrally or separately from a copier, printer or similar image forming apparatus for executing sorting, stacking, jogging, stapling, center stapling and binding, punching or similar processing with sheets carrying images thereon and then discharging the sheets, and an image forming system made up of the sheet finisher and image forming apparatus.
2. Description of the Background Art
A sheet finisher configured to automatically execute processing of the kind described above with sheets sequentially driven out of an image forming apparatus has been proposed in various forms in the past. Particularly, various methods have been proposed for the movement of a stapler. Japanese Patent Laid-Open Publication No. 9-235070, for example, discloses a sheet finisher including a stapler mounted on a guide shaft, which extends between the front and rear side walls of a staple tray. The stapler is movable in a direction perpendicular to the direction of sheet conveyance and slidable in the direction of sheet conveyance as well.
More specifically, in the above conventional sheet finisher, after the trailing edge of a sheet stack has been positioned by being abutted against a reference fence located below the staple tray, a hook affixed to a timing belt or similar band-like drive transmitting means lifts the trailing edge of the sheet stack for thereby causing the sheet stack to be driven out to a tray. The stapler is allowed to slide in the direction of sheet conveyance such that it does not contact a pulley or similar rotary member, which drives the drive transmitting means, when moving in the direction perpendicular to the direction of sheet conveyance.
However, to allow the stapler to move in both of the direction of sheet conveyance and the direction perpendicular thereto, the conventional sheet finisher needs a number of parts and is therefore sophisticated in configuration. In addition, such a number of parts increase the cost of the sheet finisher.
Technologies relating to the present invention are also disclosed in, e.g., Japanese Patent Laid-Open Publication Nos. 2000-169028, 2001-171898 and 2002-273705.